Mechanical Properties And Microscopic Mechanism Of Composite Modified Iron Tailings Powder

With the exploitation of global mining resources and the aggravation of environmental pollution,the recycling of iron tailings powder has drawn increasing attention from the society.As a common curing agent,cement can greatly improve the strength of iron tailings in a short time.However,the existing research shows that the improvement of the length and age strength of the reinforced body by cement is always limited.As the most valuable nanomaterials for commercial application,and fly ash as a common industrial waste,the organic combination of them and iron tailings powder will expand the range of iron tailings powder recycling.In view above the situation,this paper mainly studies the geotechnical test.The characteristics of unconfined compressive strength,small strain modulus and microscopic strengthening mechanism of cement iron tailing powder,nano-modified cement iron tailing powder and cement fly ash iron tailing powder were explored.The influencing factors and changing rules of the strength,stiffness and small strain characteristics of the three modified iron tailing powder were compared and analyzed,which provided basic test data and mechanism analysis for the application of the composite modified iron tailing powder in engineering.?1?The improvement of unconfined compressive strength of cement iron tailing powder with different cement content at different curing ages.The strength of cement iron tailing powder increases with the increase of cement content at 7 days and 28 days.At 56and 90 days of curing age,the unconfined compressive strength of 5%and 10%cement iron tailings powder increases with the development of age.The unconfined compressive strength of cement iron tailing powder with cement content of 20%and 30%decreases originally and then increases with curing age.?2?Within different curing ages,different material combinations can improve the unconfined compressive strength of cement iron tailing powder.The unconfined compressive strength of nano cement iron tailing powder and cement fly ash iron tailing powder increases continuously with the growth of age at 7 days and 28 days.At the curing ages of 56 days and 90 days,the unconfined compressive strength of nano-cement modified iron tailings powder increases first and then decreases with the age,and the unconfined compressive strength of cement fly ash iron tailings powder increases with the age.The strength of nano-cement iron tailing powder and cement fly ash iron tailing powder meet up with the relevant specification requirements.?3?The failure strain of cement iron tailing powder and nano-cement iron tailing powder increases first and then decreases with age respectively.The failure strain of cement fly ash iron tailing powder decreases first and then increases with curing age.On the basis of defining the variation rules of the unconfined compressive strength and failure strain of the three modified iron tailings powder,the relationship between the secant modulus E₅₀and unconfined compressive strength q_u of the three modified iron tailings powder under the influence of different factors is constructed.?4?In the range of small strain(10^-6?10^-4),different material combinations can improve the small strain stiffness characteristics of iron tailings at different curing ages.The increase of maximum dynamic shear modulus G_max of cement iron tailing powder is sensitive to the change of cement content and confining pressure.The G_max of nanometer cement iron tailing powder is sensitive to the content of nano-clay.Gmax of fly ash cement iron tailing powder is sensitive to curing age and confining pressure.The maximum damping ratio?_max and minimum damping ratio?_min of the cement iron tailing powder are sensitive to the cement content.The?_max of nano-cement iron tailings is sensitive to the content of nano-clay while?_min is sensitive to the content of nano-clay at the curing age of7 days and 14 days.The?_max of cement fly ash iron tailing powder is sensitive to fly ash content while the?_min show different characteristics under the influence of different factors.?5?Scanning electron microscope?SEM?test results showed that when the curing age is 7 days,the microstructural surfaces of cement iron tailings powder and nano-cement iron tailings powder are relatively stable,and the addition of fly ash to the microstructure surface of cement iron tailings powder has limited improvement.When the curing age is28 days,the microstructure surface of cement iron tailings powder and nano-cement iron tailings powder expands with the development of age,the microstructure surface of cement fly ash iron tailings powder is dense,and the pores between the pellets are significantly reduced compared with that at 7 days.X-ray diffraction?XRD for short?and energy dispersion spectroscopy?EDS?test results show.The incorporation of nano-clay and fly ash has refined the grain size of cement iron tailings powder.